Sunglasses having a pair of polarizing lens elements disposed in each eye opening in which one lens of each pair is rotatable with respect to the other lens are well known. Various designs and structures have been used in the prior art to support rotatably the lenses and to effect the simultaneous rotation of the lenses. The prior art structures and mechanisms suffer from a variety of deficiencies as explained below.
One such prior art structure and mechanism is shown in U.S. Pat. No. 3,944,346 Shindler. This structure is comprised of front and rear frame sections, with each section carrying two lens elements disposed in respective lens openings. The rear section, which carries a rotatable lens, is attached to the front section by a threaded screw and nut, or other fastener, located at the bridge of the frames, immediately above the nose. A lens rotating mechanism made of a wire is bent at either end and extends into holes in either rotatable lens, such that both circular lenses may be simultaneously rotated by the horizontal translation and slight rotation of the wire as it is slide from side to side. The movement is effected through the use of a handle which extends forwardly from the front of the frame through a generally horizontal slot formed through the front of the frame.
This structure somewhat typifies the numerous problems with the prior art structures. The two piece frame construction represents an overly complex structure for retaining and rotating the lenses. The complexity of the frame design creates difficulty in the manufacture of the fame. Additionally, the construction of the lens rotating mechanism in combination with the two piece frame limits the ability to adapt the design to aesthetically pleasing, stylish frames. For example, in addition to the unattractive connection between the front and rear frame sections, there is the obtrusive forwardly protruding handle for controlling the rotation of the lenses, all of which are clearly visible to the public when the frames are worn. Additionally, with the '346 structure, the mechanism used for effecting the rotation of the lenses extends into the lens opening where it can distract the wearer.
The prior art glasses disclosed in the '346 patent show circular lenses having peripheral edges which are completely enclosed by the grove in the rear frame section. This effectively precludes the use of more than one set of rotatable lenses. The construction disclosed in the '346 patent permits only a single range within which to vary the orientation of the rotating lenses with respect to the fixed lenses.
As is well known, the amount of light which can pass through a pair of polarizing lenses may be varied by changing the relative orientation of the "axes of polarization" of the two lenses. Polarizing lens elements are available in a variety of absorption values and characteristics. The ability to use more than one set of rotatable lenses would allow the wearer to select rotatable lens elements of different darkness for varying conditions.
In sunglasses having two spaced apart lenses in each lens opening, dirt can get in between the lenses, requiring that the inner and outer surfaces of both lenses be cleaned frequently. In the prior art glasses, such as that shown in the '346 patent, it is necessary to disassemble the front and rear frame sections in order to clean the lenses. Not only is this cumbersome, but it can be quite time consuming.
There is a need in the art for sunglasses which are stylish, simple to manufacture and use, and which can allow the use of a variety of interchangeable lenses while still permitting those lenses to rotate so as to take advantage of the change in light transmission as a result of changes in the orientation of the axes of polarization. The lenses need to be easily removed and replaced, which not only aides in interchangability but greatly simplifies cleaning the lenses. There is also a need in the art to provide for the easy disassembly of any frame members which might be necessarily removed in order to change or clean the lenses.